Patent Document 1 discloses an optical material composed of a thiourethane resin. Furthermore, Patent Document 2 discloses an optical material composed of polythiourethane produced by the use of a prescribed catalyst. According to the documents, these resins have a high refractive index and high transparency, and can be suitably used for optical lenses among optical materials.
However, the documents do not disclose physical properties when a thiourethane resin is formed into a film at a thickness of equal to or less than 1 mm, and a method of controlling transmission of light as a whole by the use in contact with other materials in a thin film form. Furthermore, when these resins are made into a thin film, there are difficulties in coating from the viewpoint of reactivity of a raw material, and a method of obtaining a stable film or thin film is not reviewed either.
Patent Document 3 discloses an optical material having a structure in which a polythiourethane skeleton is introduced into a polythiocarbonate skeleton. According to the document, the resulting film from the optical material is excellent in optical properties such as high refractive index, high Abbe's number and the like, and further excellent in mechanical properties such as tensile properties, high elasticity and the like. The document discloses a case in which a film is formed from the aforementioned optical material by a casting (solution casting) method of a resin solution.